Grain and other relatively free-flowing, finely divided materials are frequently stored in air-tight silos or storage structures and are unloaded from the bottom of the silo through use of a bottom unloader. The copending U.S. patent application Ser. No. 205,461, filed Nov. 10, 1980, now U.S. Pat. No. 4,386,695, discloses a bottom unloader mechanism which includes an auger-type sweep arm that is mounted to rotate about the center of the silo and undercut the stored material and convey it to the center of the silo where it is delivered to a discharge auger that operates in a radially extending trough in the silo foundation. In an unloader of the type described in the aforementioned patent application, the inner end of the sweep arm is mounted on a turntable and is rotated in increments around the silo by a ratchet and pawl mechanism which interconnects a drive unit on the exterior of the silo with a drive shaft. The inner end of the drive shaft carries a drive sprocket that engages a series of drive pins on the turntable to rotate the turntable and the sweep arm around the silo. In addition, rotation of the discharge auger is transmitted through a gear drive located in the inner end of the trough to the sweep arm to thereby rotate the sweep arm about its axis as it sweeps about the silo.
With a bottom unloading mechanism of the type described in the above mentioned patent application, the stored material is delivered by the sweep auger to the center of the silo where it falls into the inner end of the trough. As the drive sprocket and turntable are located in the inner end of the trough, they are in continual contact with the stored material.
When dealing with a finely divided stored material, such as ground ear corn, grain, meat meal, starch, and the like, there is a tendency for the stored material to be compacted and build up in the turntable drive mechanism. A buildup of the compacted material in the drive elements of the turntable can result in stoppage or breakdown of the drive mechanism, and to relieve the jamming problem, it is necessary to remove the entire bottom unloading mechanism from the silo.